Design and performance of a stable linear retarder

Abstract

The National Institute of Standards and Technology (NIST) has developed a nominally quarter-wave linear retarder for wavelengths near 1.3 mum that is stable within +/-0.1 degrees retardance over a range of wavelength, input angle, temperature, and environmental variations. The device consists of two concatenated Fresnel rhombs made from a low stress-optic-coefficient glass that minimizes the residual birefringence from machining and packaging. Device machining, assembly, and antireflection coating tolerances are discussed, and the theoretical performance is compared with measurements. Humidity can modify retardance of the total-internal-reflection surfaces; we discuss packaging that mitigates this effect and provides an estimated 10-year lifetime for the device. Several measurement methods were intercompared to ensure that the device retardance can be measured with an uncertainty less than 0.1 degrees . Similar retarders will be certified by NIST and made available as Standard Reference Materials.

Fresnel rhombs as achromatic phase shifters for infrared nulling interferometry: first experimental results

“…If we assume a uniform distribution of ¢(t) in the [O, 27r] interval, we find the probability density function for /j,J ( R): P( Jj,J). 20 The mean error in this case is zero. In the case of r5 0 = 90° and of small reflectance, the standard deviation is about ,/2.R.…”

“…For this reason, we chose the double rhomb configuration for its known insensitivity to incidence angle variations. 20 Indeed, the pairs of reflections in the two rhombs are complementary (see Fig. 2); an increase in the first two TIR angles due to departure from nominal incidence leads to a decrease in the last two angles.…”

“…Note that the influence of induced birefringence on the phase shift is proportional to the stress-optic coefficients but inversely proportional to the wavelength. Therefore, as the stress-optic coefficients do not change so much from the visible (632.8 nm) to the Darwin wavelength range ( [6][7][8][9][10][11][12][13][14][15][16][17][18] µm), the birefringence error is divided by ten at the wavelengths the rhomb has been designed for. …”

“…Therefore, as the length of the path at the output of the rhomb is different for the main beam and for the ghosts, the different beams interfere together and strongly impact the retardance. Indeed, according to , 20 for a perfectly coherent source, the change in retardance resulting from spurious reflections Jj,J(R) can be found by summing up the individual fields that contribute to the transmitted fields. For a reflectance R, we have…”

Infrared achromatic phase shifters using modulated total internal reflection

“…These original components fit in the technological evolution of the well-known Fresnel rhomb technology. 3 Our theoretical calculations using the Rigorous Coupled Wave Analysis point to promising results.…”